xxii GENERAL SUMMARY OF SCDSNTIEIC AND 



tary and economical considerations. Until recently a sub- 

 stance originally known as an incrustation upon the sands in 

 the vicinity of .the Temple of Jupiter Ammon, and hence call- 

 ed 8al ammoniac , was the principal source of the small amount 

 of volatile alkali required in medicine and the arts. A great 

 change has recently taken place in the commercial value of 

 this article. Ammonia is now largely consumed in the arti- 

 ficial production of ice, as a motive power, as a fire extin- 

 guisher, as a fertilizer, and in numerous arts and industries. 

 Its enormous production from gas-house liquors, from the 

 spent vapors of the lagoons of Tuscany, from the residues of 

 the refinery of Chile saltpetre, from crude borax, and from vol- 

 canic incrustations, is one of the features of modern industry. 



The study and practical application of the products derived 

 from the distillation of coal, wood, and petroleum is still pros- 

 ecuted with success, and so much literature has accumula- 

 ted in this branch of chemistry that a systematic and classi- 

 fied list is greatly to be desired. The aniline industry has 

 increased in proportion, and we have new artificial colors to 

 be added each year. Artificial alizarine would seem to be an 

 accomplished fact, and the only vegetable dye which remains 

 for the chemist to imitate is indigo. Carbolic acid, paraffine, 

 and glycerine are becoming familiar to every body, and their 

 uses have been greatly extended during the year. 



We have not the space to enumerate all that has been dis- 

 covered in coal-tar and petroleum, and must content ourselves 

 with the above reference to this branch of industry. 



In the working of ores and metals many changes have been 

 introduced, and metals which for their rarity and cost were 

 formerly classed among the luxuries, are now of common use, 

 and great aids to the comforts of civilization. Among these 

 we may count the common production and use of zinc ; the 

 increased production of aluminium and magnesium ; the 

 cheapening of iron and steel by the Bessemer process; the 

 free use of nickel for plating ; the appearance of manganese 

 upon the stage to be alloyed with copper, and the cheap man- 

 ufacture of sodium as compared with former prices. The 

 disintegration of lead ores by zinc has been developed and 

 applied within a recent period. In all metallurgical opera- 

 tions there has been hitherto a serious Avaste in the accumu- 

 lations of the flues and in the slags. Much of this loss is 



